Cannot render plot inside dynamic UI, when using a shiny module

Normally, Shiny has no problem generating plots from within UIs that the user calls reactively, but I've noticed that when using a shiny module to dynamically generate the UI, the plot does not appear.

Below is a minimal example of a modularized shiny app that reproduces the problem; it is supposed to generate a ui with a plot in it when the user presses the "go" button: